Snow and sleet on walkways make for hazardous, slippery conditions for pedestrians. Typically, ameliorative measures comprise shoveling deep snow from the path and scattering sand or salt over the remaining icy layer to promote melting. However, the sand and salt still require cooperation from the weather; although they promote melting at low temperatures, when the air temperature is too cold, the ice won't melt readily so the sand and salt are not effective.
As an alternative, electrically heated devices have been employed. One solution, offering a permanently installed de-icing device, is a precast heating panel having a flexible electric heating element embedded in fiber-enforced mortar which serves as the walkway, itself (U.S. Pat. No. 4,564,745 to Deschenes). Similarly, U.S. Pat. No. 4,814,580 to Carageorge describes a thermal walkway built of bricks having embedded electrical heating elements. Installation of these systems is costly. Moreover, if the electrical heating element fails, repair requires breaking through the existing walkway to reach the electrical parts. Further, these devices are only useful where permanently-installed devices are feasible. They do not offer a means to prevent ice build-up on existing walkways and steps.
Electrically heated de-icing devices that are simply laid over existing walkways provide a solution that has more widespread commercial appeal as a method of clearing ice from entranceways. One example of such a device is embodied in a flexible mat composed of two sheets with a heating element in between. However, these particular devices are unsatisfactory when there is heavy snowfall. In such circumstances, people find it necessary to shovel off the deep snow, relying on the heating element merely to prevent an icy layer from forming. The flexible mats are susceptible to damage from the snow shoveling implements; the mat itself can be pierced, thus damaging the electrical heating element inside. Since the mats are made of flexible material, the heating elements within are subject to wear from the flexing and bending resulting from the weight of persons walking on the mats. Furthermore, a rubber mat is not a good thermal conductor, so means for conducting the heat to the surface of the mat are required.
Some de-icing mats have been made more protective of the electrical heating elements inside by substituting for the flexible sheets, interleaved link elements, which have hollow metal tubes containing electrical heating elements sealed within. This serves to protect the electrical wires from sharp instruments, but it makes shoveling the snow extremely difficult because it presents an uneven surface for the snow shovel. Furthermore, a mat composed of hollow tubes does not provide very safe footing.
What is needed is a de-icing device that can be placed over existing walkways, including steps, can be employed compatibly with snow shoveling implements, is not susceptible to damage by sharp implements, provides said footing and can be replaced at low cost.